Promoter- and activator-specific requirements for BUR6. (A) Northern blot analysis of selected transcripts from wild-type (WT), bur6–1, and spt15–601 strains grown under uninduced and induced conditions as indicated. (B) Activation domain-specific requirement for BUR6 with LexA-activation domain fusions. BUR6+ and bur6–1 strains containing a LacZ reporter driven by a LexA-binding site and a plasmid expressing either the LexA DNA-binding domain or the LexA DNA-binding domain fused to the activation domains of Hap4, Gal4, and Gcn4. β-Galactosidase assays were performed in triplicate, with the average LacZ activity and standard deviations shown.